Add COM_DLL_EXCEPT to specifiy exceptions for data link loss failsafe

src/modules/commander/commander_params.c

@@ -615,7 +615,7 @@ PARAM_DEFINE_INT32(NAV_RCL_ACT, 2);
  * Specify modes in which RC loss is ignored and the failsafe action not triggered.
  *
  * @min 0
- * @max 31
+ * @max 7
  * @bit 0 Mission
  * @bit 1 Hold
  * @bit 2 Offboard
@@ -623,6 +623,20 @@ PARAM_DEFINE_INT32(NAV_RCL_ACT, 2);
  */
 PARAM_DEFINE_INT32(COM_RCL_EXCEPT, 0);
 
+/**
+ * Datalink loss exceptions
+ *
+ * Specify modes in which datalink loss is ignored and the failsafe action not triggered.
+ *
+ * @min 0
+ * @max 7
+ * @bit 0 Mission
+ * @bit 1 Hold
+ * @bit 2 Offboard
+ * @group Commander
+ */
+PARAM_DEFINE_INT32(COM_DLL_EXCEPT, 0);
+
 /**
  * Set the actuator failure failsafe mode
  *

src/modules/commander/failsafe/failsafe.cpp

@@ -452,8 +452,9 @@ void Failsafe::checkStateAndMode(const hrt_abstime &time_us, const State &state,
 
 	// Do not enter failsafe while doing a vtol takeoff after the vehicle has started a transition and before it reaches the loiter
 	// altitude. The vtol takeoff navigaton mode will set mission_finished to true as soon as the loiter is established
-	const bool ignore_link_failsafe = state.user_intended_mode == vehicle_status_s::NAVIGATION_STATE_AUTO_VTOL_TAKEOFF
+	const bool ignore_any_link_loss_vtol_takeoff_fixedwing = state.user_intended_mode ==
-					  && in_forward_flight && !state.mission_finished;
+			vehicle_status_s::NAVIGATION_STATE_AUTO_VTOL_TAKEOFF
+			&& in_forward_flight && !state.mission_finished;
 
 	// Manual control (RC) loss
 	if (!status_flags.manual_control_signal_lost) {
@@ -470,8 +471,10 @@ void Failsafe::checkStateAndMode(const hrt_abstime &time_us, const State &state,
 	const bool rc_loss_ignored_takeoff = (state.user_intended_mode == vehicle_status_s::NAVIGATION_STATE_AUTO_TAKEOFF ||
 					      state.user_intended_mode == vehicle_status_s::NAVIGATION_STATE_AUTO_VTOL_TAKEOFF)
 					     && (_param_com_rcl_except.get() & (int)ManualControlLossExceptionBits::Hold);
+
 	const bool rc_loss_ignored = rc_loss_ignored_mission || rc_loss_ignored_loiter || rc_loss_ignored_offboard ||
-				     rc_loss_ignored_takeoff || ignore_link_failsafe || _manual_control_lost_at_arming;
+				     rc_loss_ignored_takeoff || ignore_any_link_loss_vtol_takeoff_fixedwing
+				     || _manual_control_lost_at_arming;
 
 	if (_param_com_rc_in_mode.get() != int32_t(RcInMode::StickInputDisabled) && !rc_loss_ignored) {
 		CHECK_FAILSAFE(status_flags, manual_control_signal_lost,
@@ -479,10 +482,23 @@ void Failsafe::checkStateAndMode(const hrt_abstime &time_us, const State &state,
 	}
 
 	// GCS connection loss
-	const bool gcs_connection_loss_ignored = state.user_intended_mode == vehicle_status_s::NAVIGATION_STATE_AUTO_LAND ||
+	const bool dll_loss_ignored_land = state.user_intended_mode == vehicle_status_s::NAVIGATION_STATE_AUTO_LAND
-			state.user_intended_mode == vehicle_status_s::NAVIGATION_STATE_AUTO_PRECLAND || ignore_link_failsafe;
+					   || state.user_intended_mode == vehicle_status_s::NAVIGATION_STATE_AUTO_PRECLAND;
 
-	if (_param_nav_dll_act.get() != int32_t(gcs_connection_loss_failsafe_mode::Disabled) && !gcs_connection_loss_ignored) {
+	const bool dll_loss_ignored_mission = state.user_intended_mode == vehicle_status_s::NAVIGATION_STATE_AUTO_MISSION
+					      && (_param_com_dll_except.get() & (int)DatalinkLossExceptionBits::Mission);
+	const bool dll_loss_ignored_loiter = state.user_intended_mode == vehicle_status_s::NAVIGATION_STATE_AUTO_LOITER
+					     && (_param_com_dll_except.get() & (int)DatalinkLossExceptionBits::Hold);
+	const bool dll_loss_ignored_offboard = state.user_intended_mode == vehicle_status_s::NAVIGATION_STATE_OFFBOARD
+					       && (_param_com_dll_except.get() & (int)DatalinkLossExceptionBits::Offboard);
+	const bool dll_loss_ignored_takeoff = (state.user_intended_mode == vehicle_status_s::NAVIGATION_STATE_AUTO_TAKEOFF ||
+					       state.user_intended_mode == vehicle_status_s::NAVIGATION_STATE_AUTO_VTOL_TAKEOFF)
+					      && (_param_com_dll_except.get() & (int)DatalinkLossExceptionBits::Hold);
+
+	const bool dll_loss_ignored = dll_loss_ignored_mission || dll_loss_ignored_loiter || dll_loss_ignored_offboard ||
+				      dll_loss_ignored_takeoff || ignore_any_link_loss_vtol_takeoff_fixedwing || dll_loss_ignored_land;
+
+	if (_param_nav_dll_act.get() != int32_t(gcs_connection_loss_failsafe_mode::Disabled) && !dll_loss_ignored) {
 		CHECK_FAILSAFE(status_flags, gcs_connection_lost,
 			       fromNavDllOrRclActParam(_param_nav_dll_act.get()).causedBy(Cause::GCSConnectionLoss));
 	}

src/modules/commander/failsafe/failsafe.h

@@ -59,6 +59,12 @@ private:
 		Offboard = (1 << 2)
 	};
 
+	enum class DatalinkLossExceptionBits : int32_t {
+		Mission = (1 << 0),
+		Hold = (1 << 1),
+		Offboard = (1 << 2)
+	};
+
 	// COM_LOW_BAT_ACT parameter values
 	enum class LowBatteryAction : int32_t {
 		Warning = 0,        // Warning
@@ -193,6 +199,7 @@ private:
 					(ParamInt<px4::params::NAV_DLL_ACT>) 	_param_nav_dll_act,
 					(ParamInt<px4::params::NAV_RCL_ACT>) 	_param_nav_rcl_act,
 					(ParamInt<px4::params::COM_RCL_EXCEPT>) _param_com_rcl_except,
+					(ParamInt<px4::params::COM_DLL_EXCEPT>) _param_com_dll_except,
 					(ParamInt<px4::params::COM_RC_IN_MODE>) _param_com_rc_in_mode,
 					(ParamInt<px4::params::COM_POSCTL_NAVL>) _param_com_posctl_navl,
 					(ParamInt<px4::params::GF_ACTION>)  	_param_gf_action,